This application is based on an application No. 2000-222046 filed in Japan, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to an automatic document feeding apparatus, and more particularly to an improved automatic document feeding apparatus to stabilize a document transportation state at a document reading station.
2. Description of the Related Art
With reference to FIGS. 1 through 3, the following description will describe a conventional automatic document feeding apparatus adapted to a digital copying machine. FIG. 1 is a sectional front view showing a document transportation path in the automatic document feeding apparatus, FIG. 2 is a sectional plan view showing a framework of the automatic document feeding apparatus, and FIG. 3 is a sectional side view of the automatic document feeding apparatus, each being a diagrammatic illustration.
With reference to FIG. 1, an unillustrated document table is placed above a horizontal stay 1, and a document placed on the document table is fed by a pre-feeding roller 2 to be transported to a pair of resist rollers 4 by a pair of paper feeding rollers 3. The document is suspended by the pair of resist rollers 4, and then transported further from the pair of resist rollers 4, after which the document is discharged by a pair of discharging rollers 6 by way of a reading section 5 as is indicated by an arrow.
The pre-feeding roller 2, the pair of paper feeding rollers 3, the pair of resist rollers 4, and the pair of discharging rollers 6 are all enclosed in a transportation unit 7 indicated by a broken line. In other words, the automatic document feeding apparatus includes the transportation unit 7, which is unitized for ease of fabrication and assembly.
With reference to FIGS. 2 and 3, a front-end plate 8 is provided fixedly at the front end of the stay 1 and a rear-end plate 9 is provided fixedly at the rear end of the stay 1. The stay 1, front-end plate 8, and rear-end plate 9 form the framework of the automatic document feeding apparatus.
A first motor 10 for driving the pre-feeding roller 2 and the pair of paper feeding rollers 3, and a second motor 11 for driving the pair of resist rollers 4 and the pair of discharging rollers 6 are mounted on the rear-end plate 9.
In the automatic document feeding apparatus arranged in the above manner, two heavy motors 10 and 11 are unevenly provided at the rear end, and as a result, a load is applied to the rearward portion alone. This causes a longitudinal load imbalance on the document at the reading section 5. The load imbalance on the document at the reading section 5 may distort the document while it is fed forward.
On the other hand, when an operator sets a document on the reading table manually and makes a copy without using the automatic document feeding function, the operator closes and opens the automatic document feeding apparatus. Because the entire automatic document feeding apparatus is quite heavy, a spring such that pushes the automatic document feeding apparatus in an opening direction is incorporated in a hinge 12 provided at the rearward portion, so that the operator can manipulate the automatic document feeding apparatus easily. The automatic document feeding apparatus is kept pushed in the opening direction by the pushing force of the spring. Hence, the stay 1 may cause deflection as it deteriorates with time. Because the transportation unit 7 is provided fixedly to the stay 1, deflection of the stay 1 causes the transportation unit 7 to be displaced from a predetermined position, which poses a problem that a document transportation direction is displaced by the transportation unit 7.
Further, when deflection of the stay 1 makes it difficult for the transportation unit 7 to closely adhere onto the reading table, the operator has to press the front end of the automatic document feeding apparatus hard against the reading table to closely adhere the transportation unit 7 to the reading table. For this reason, at the bottom of the front end, the conventional automatic document feeding apparatus is occasionally provided with a magnet that develops a force to attract the front end of the automatic document feeding apparatus closely to the reading table. The attracting force of the magnet contributes to close adhesion of the transportation unit 7 to the reading table. However, the operator has to apply a large force when he opens the automatic document feeding apparatus, which poses a problem that the apparatus becomes less easy to manipulate.
The present invention is devised with the above backgrounds, and has a principal object to provide an automatic document feeding apparatus capable of transporting a document in a satisfactory manner.
Another object of the present invention is to provide an improved automatic document feeding apparatus such that a load is applied evenly onto a document being transported.
Still another object of the present invention is to provide an automatic document feeding apparatus that is easy to manipulate, in particular, easy to open and close.
The present invention relates to an automatic document feeding apparatus characterized in that a transportation unit (a unit enclosing a pre-feeding roller, a pair of paper feeding rollers, a pair of resist rollers, a reading section, a pair of discharging rollers, etc.) is attached to a framework forming member (a stay, a front-end plate, a rear-end plate, etc.) not fixedly, but in such a manner that at least a rearward end of the transportation unit is capable of displacements in a vertical direction (in a direction to move towards or away from a reading table) with respect to the framework member.
The automatic document feeding apparatus attached to a copying machine or the like is frequently opened and closed with respect to the main body housing of the copying machine or the like. More specifically, because the copying machine or the like does not always operate in the automatic document feeding mode and the documents are often set manually, the automatic document feeding apparatus is opened and closed quite frequently. Hence, if the framework forming member of the automatic document feeding apparatus causes deflection, the position of the transportation unit on the reading table changes slightly when the automatic document feeding apparatus is closed. Such a change in the position of the transportation unit on the reading table adversely affects the document feeding and reading jobs.
According to the arrangement of the present invention, however, even when the framework forming member causes deflection, because the transportation unit is attached to the framework forming member in such a manner that it is capable of displacements, the deflection caused on the framework member will not adversely affect an attachment state of the transportation unit. Consequently, the positioning of the transportation unit is carried out at an exact predetermined position on every occasion, and a document is transported in a satisfactory manner.
According to a preferred embodiment of the present invention, the rearward end of the transportation unit is attached to the framework forming member in such a manner that it is capable of displacements in a vertical direction, and the frontward end of the transportation unit is attached to the framework forming member in such a manner that it is capable of displacements in the longitudinal direction. Hence, the rearward end of the transportation unit remains at a predetermined position in the longitudinal direction with respect to the framework forming member all the time. Moreover, when the framework forming member causes deflection in the longitudinal direction, the transportation unit remains unaffected by such deflection and maintains a certain attachment state, thereby making it possible to transport a document in a satisfactory manner.
These and other objects of the invention and the arrangements of the invention will become more apparent from the following detailed description with reference to the accompanying drawings.